The goal of these studies is to develop efficient methods for complementing the genetic defects in the LDL receptor and apoE genes as an approach to gene therapy for familial hypercholesterolemia. Our studies are based on the use of the new class of high titer retroviral vectors pseudotyped with the G protein of vesicular stomatitis virus (VSV-G) recently developed in our laboratory. Our first major goal is to develop much more efficient methods of producing the pseudotyped vectors, aiming principally at the development of stable packaging cell lines that express the toxic G protein conditionally. Using these vectors, we will pursue direct in vivo models for correcting the genetic defects in the liver of hypercholesterolemic mice with LDL receptor and apoE deficiency. The potential for this approach has been established by our recent demonstration of highly efficient infection (>40% transduction efficiency) of hepatocytes in the neonatal mouse liver by a pseudotyped vector. We will also pursue an ex vivo model based on the implantation of grafts of genetically modified hepatocytes embedded in reticulated polyurethane. Finally, we will examine the potential for insertional mutagenesis in cells infected with high titer preparations of the pseudotyped vectors.